The present invention relates to electrocardiography (ECG) and more particularly to rhythm analysis of electrocardiographic signals.
Various devices are known for monitoring heart functions and analyzing signals to assess and aid in diagnosis of a patient's heart condition. Many of these devices make use of the QRS complex region of the ECG waveform to detect heartbeats and to characterize the beat as falling within one of several morphological categories for a particular patient, such as normal or a plurality of abnormal categories. Often these devices are equipped with an alarm which is triggered when the device has detected certain predetermined electrocardiographic patterns which correspond to certain dangerous heart conditions such as ventricular fibrillation, for example. Examples of above described prior art devices are found in U.S. Pat. Nos. 3,759,248; 4,023,564; 4,336,810; and 4,360,030.
However, despite the many benefits of the prior art devices, the state of the art for heartbeat rhythm analysis is not without its problems. The timing, shape, and other characteristics of the QRS complex vary greatly among patients and it is highly desirable that ECG monitoring and analysis devices be designed to detect, characterize, store and display a wide variety of ECG signals relating to various types of heart conditions and to provide trend data associated with such conditions. Further, it is common in the state of the art today to find device false alarm rates in the range of 30% to 50% due to effects of noise. Such noise includes 60 cycle superimposition and other electromagnetic interference from electronic equipment found in hospitals today. Also, false alarms by state of the art devices are triggered by responding to high frequency muscle noise occurring concurrent with heart contractions. Also, abrupt base line shifts brought on by patient movement and respiration cause false alarms.